The present invention relates generally to power generation equipment such as fuel cell assemblies, and particularly to thermal management of fuel cell assemblies, such as solid oxide fuel cell assemblies.
Thermal energy is generated in a fuel cell from the reaction of a fuel and an oxidant. Fuel cells, such as solid oxide fuel cells operate at a temperature typically between about 600° C. to about 1300° C. Such fuel cells, typically used in power generation applications, are disposed within a pressurized container. However, maintaining structural integrity of such container poses challenges, particularly as it is desirable to fabricate the container from available materials which are relatively inexpensive but that can nevertheless withstand the specified temperature range during operation.
A particular challenge in thermal management of fuel cells is to maintain a certain maximum temperature, or lower, of the container. Another difficulty resides in maintaining fairly uniform thermal gradients in the container, both through the thickness of the container wall and associated structures, and along the container wall (e.g. in lateral directions). Such thermal gradients can generate thermal hot spots at localized regions in the container, and cause structural and material problems, due to differential thermal expansion, for example.
Certain existing fuel cell designs make use of insulation within a part of the container, typically integral with the container wall. Other designs form cooling channels within the container wall itself. However, conventional fuel cell applications that use such integral cooling channels generally cannot maintain an isothermal condition throughout the container, and do not reduce the heating of the container wall. Additionally, removing waste heat flux generated by the fuel cell outside the fuel cell assembly can result in poor thermal performance of the fuel cell assembly. Similarly, partitions or channels of the type used in existing arrangements can actually cause substantial thermal gradients along the container wall, resulting in the type of differential heating that should be avoided.
Accordingly, there is a need in the art for an improved thermal management system for fuel cell assemblies, which can maintain more uniform thermal gradients of the container, reduce the temperature of the container itself, and enhance the desired thermal efficiency of the fuel cell assembly.